This invention relates to an improvement on straightedges and the like. Previously, straightedges have been used to approximate perpendicular lines, extend lines, line up parallel lines, etc. However, these lines are only approximate. Really straight extended lines, really perpendicular lines and really parallel lines are much more time consuming to construct with old-style straightedges. This is due to the fact that the user often only lines up lines by sight, and also due to the fact that when a using an ordinary straightedge, it is difficult to line up the writing instrument at exactly the same distance from the edge of the straightedge every time.
It is the purpose of this present invention, therefore, to mitigate and/or obviate the above-mentioned drawbacks in the manner set forth in the detailed description of the preferred embodiment.